On cigarette manufacturing machines, a continuous bead of tobacco is fed, normally by means of a suction conveyor belt, onto a forming beam, at the input of which, the tobacco bead is fed onto a continuous paper strip which is gradually folded transversely about the bead along the forming beam to form a continuous cigarette rod.
To maintain a constant amount of tobacco along the bead, the machine is equipped with a shaving device, which interferes with the bead as this is fed towards the forming beam, so as to obtain a substantially constant bead section.
U.S. Pat. No. 5,325,874 describes a shaving device comprising two parallel, counter-rotating disks with respective peripheral portions tangent to each other at a point along the path of the tobacco bead. The counter-rotating disks have sharp edges for detaching the surplus tobacco from the bead, which surplus is then removed by a cutter and fed to the input of a tobacco collecting device.
Though highly efficient, the above shaving device has a relatively bulky structure, both crosswise to the tobacco bead, on account of the two side by side counter-rotating disks, and parallel to the tobacco bead, on account of the cutter for removing the surplus tobacco detached by the two counter-rotating disks.
The above shaving device also has a fairly complex, and therefore high-cost, structure on account of the surplus tobacco cutter.
One solution to the above drawback is proposed in U.S. Pat. No. 2,660,178, which describes a shaving device having two superimposed blades oscillating with respect to each other in a direction crosswise to the traveling direction of the tobacco bead. Each blade has a serrated edge contacting the tobacco bead, and which cooperates with the serrated edge of the other blade to cut the surplus tobacco.
Though relatively compact, the reciprocating movement of the above shaving device results in severe vibration--especially at the high operating speeds of modern manufacturing machines--which in turn reduces the working life of the device itself.